Microporous material

ABSTRACT

Microporous materials that include thermoplastic organic polyolefin polymer (e.g., ultrahigh molecular weight polyolefin, such as polyethylene), particulate filler (e.g., precipitated silica), and a network of interconnecting pores, are described. The microporous materials of the present invention possess controlled volatile material transfer properties. The microporous materials can have a density of at least 0.8 g/cm 3 ; and a volatile material transfer rate, from the volatile material contact surface to the vapor release surface of the microporous material, of from 0.04 to 0.6 mg/(hour*cm 2 ). In addition, when volatile material is transferred from the volatile material contact surface to the vapor release surface, the vapor release surface is substantially free of volatile material in liquid form.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/761,020, filed Apr. 15, 2010, incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to microporous materials that include,thermoplastic organic polymer, particulate filler, and a network ofinterconnecting pores. The microporous materials of the presentinvention possess controlled volatile material transfer properties.

BACKGROUND OF THE INVENTION

The delivery of volatile materials, such as fragrances (e.g., airfresheners) may be achieved by means of a delivery apparatus thatincludes a reservoir containing volatile material. The deliver apparatustypically includes a vapor permeable membrane that covers or enclosesthe reservoir. Volatile material within the reservoir passes through thevapor permeable membrane and is released into the atmosphere (e.g., air)on the atmosphere side of the membrane. Vapor permeable membranes aretypically fabricated from organic polymers and are porous.

The rate at which volatile material passes through the vapor permeablemembrane is generally an important factor. For example, if the rate atwhich volatile material passes through the vapor permeable membrane istoo low, properties associated with the volatile material, such asfragrance, will typically be undesirably low or imperceptible. If, forexample, the rate at which volatile material passes through the vaporpermeable membrane is too high, the reservoir of volatile material maybe depleted too quickly, and properties associated with the volatilematerial, such as fragrance, may be undesirably high or in someinstances overpowering.

It is generally desirable to minimize or prevent the formation of liquidvolatile material on the atmosphere or exterior side of the vaporpermeable membrane, from which the volatile material is released intothe atmosphere (e.g., into the air). Liquid volatile material that formson the exterior side of the vapor permeable membrane may collect (e.g.,puddle) within and leak from the delivery apparatus resulting in, forexample, staining of articles, such as clothing or furniture, that comeinto contact therewith. In addition, the formation of liquid volatilematerial on the exterior side of the vapor permeable membrane may resultin uneven release of volatile material from the delivery device.

Upon exposure to an increase in ambient temperature, the rate at whichvolatile material passes through the vapor permeable membrane mayincrease to an undesirably high rate. For example, a delivery apparatusthat is used within the passenger compartment of an automobile may beexposed to increases in ambient temperature. As such, minimizing theincrease in the rate at which volatile material passes through the vaporpermeable membrane, as a function of increasing ambient temperature istypically desirable.

It would be desirable to develop new microporous materials that possesscontrolled volatile material transfer properties. It would be furtherdesirable that such newly developed microporous materials minimize theformation of liquid volatile material on the exterior side or surfacethereof. In addition, the rate at which volatile material passes throughsuch newly developed microporous materials undergoes a minimal increasewith an increase in ambient temperature.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided, amicroporous material comprising:

(a) a matrix of substantially water-insoluble thermoplastic organicpolymer comprising polyolefin;

(b) finely divided, substantially water-insoluble particulate filler,said particulate filler being distributed throughout said matrix andconstituting from 40 to 90 percent by weight, based on the total weightof said microporous material; and

(c) a network of interconnecting pores communicating substantiallythroughout said microporous material;

wherein said microporous material has

-   -   a density of at least 0.8 g/cm³,    -   a volatile material contact surface,    -   a vapor release surface, wherein said volatile material contact        surface and said vapor release surface are substantially opposed        to each other, and    -   a volatile material transfer rate, from said volatile material        contact surface to said vapor release surface, of from 0.04 to        0.6 mg/(hour*cm²), and    -   wherein when volatile material is transferred from said volatile        material contact surface to said vapor release surface (at a        volatile material transfer rate of from 0.04 to 0.6        mg/(hour*cm²)), said vapor release surface is substantially free        of volatile material in liquid form.

Further, the present invention provides a microporous materialcomprising:

(a) a matrix of substantially water-insoluble thermoplastic organicpolymer comprising polyolefin;

(b) finely divided, substantially water-insoluble particulate filler,said particulate filler being distributed throughout said matrix andconstituting from 40 to 90 percent by weight, based on the total weightof said microporous material; and

(c) a network of interconnecting pores communicating substantiallythroughout said microporous material;

wherein said microporous material has

-   -   a density of less than 0.8 g/cm³,    -   a volatile material contact surface,    -   a vapor release surface, wherein said volatile material contact        surface and said vapor release surface are substantially opposed        to each other, wherein (i) at least a portion of said volatile        material contact surface has a first coating thereon,        and/or (ii) at least a portion of said vapor release surface has        a second coating thereon,    -   a volatile material transfer rate, from said volatile material        contact surface to said vapor release surface, of from 0.04 to        0.6 mg/(hour*cm²), and    -   wherein when volatile material is transferred from said volatile        material contact surface to said vapor release surface (at a        volatile material transfer rate of from 0.04 to 0.6        mg/(hour*cm²)), said vapor release surface is substantially free        of volatile material in liquid form.

Also, the present invention provides, a microporous material comprising:

(a) a matrix of substantially water-insoluble thermoplastic organicpolymer comprising polyolefin;

(b) finely divided, substantially water-insoluble particulate filler,said particulate filler being distributed throughout said matrix andconstituting from 40 to 90 percent by weight, based on the total weightof said microporous material; and

(c) a network of interconnecting pores communicating substantiallythroughout said microporous material;

wherein said microporous material has,

-   -   a volatile material contact surface,    -   a vapor release surface, wherein said volatile material contact        surface and said vapor release surface are substantially opposed        to each other, wherein (i) at least a portion of said volatile        material contact surface has a first coating thereon,        and/or (ii) at least a portion of said vapor release surface has        a second coating thereon, wherein said first coating and said        second coating are each independently selected from a coating        composition comprising poly(vinyl alcohol), and    -   a volatile material transfer rate, from said volatile material        contact surface to said vapor release surface, of at least 0.04        mg/(hour*cm²), and    -   wherein when said microporous material (i.e., the poly(vinyl        alcohol) coated microporous material) is exposed to a        temperature increase of from 25° C. to 60° C., said volatile        material transfer rate increases by less than or equal to 150        percent.

DETAILED DESCRIPTION OF THE INVENTION

As used herein and in the claims, the “volatile material contactsurface” is that surface of the microporous material that faces and,typically, is in contact with the volatile material, which is, forexample, contained in a test reservoir, as described in further detailbelow.

As used herein and in the claims, the “vapor release surface” is thatsurface of the microporous material that does not face and/or contactdirectly the volatile material, and from which volatile material isreleased into an exterior atmosphere in a gaseous or vapor form.

As used herein and in the claims, the term “(meth)acrylate” and similarterms, such as “esters of (meth)acrylic acid” means acrylates and/ormethacrylates.

As used herein and in the claims the “volatile material transfer rate”of the microporous materials, was determined in accordance with thefollowing description. A test reservoir was fabricated from a clearthermoplastic polymer, having interior volume sufficient to contain 2milliliters of volatile material such as benzyl acetate. The interiordimensions of the reservoir was defined by a circular diameter at theedge of the open face of approximately 4 centimeters and a depth of nogreater than 1 centimeter. The open face was used to determine thevolatile material transfer rate. With the test reservoir laying flat(with the open face facing upward), about 2 milliliters of benzylacetate was introduced into the test reservoir. With benzyl acetateintroduced into the test reservoir, a sheet of microporous materialhaving a thickness of from 6 to 18 mils was placed over the openface/side of the test reservoir, such that 12.5 cm² of the volatilematerial contact surface of the microporous sheet was exposed to theinterior of the reservoir. The test reservoir was weighed to obtain aninitial weight of the entire charged assembly. The test reservoir,containing benzyl acetate and enclosed with the sheet of microporousmaterial, was then placed, standing upright, in a laboratory chemicalfume hood having approximate dimensions of 5 feet (height)×5 feet(width)×2 feet (depth). With the test reservoir standing upright, benzylacetate was in direct contact with at least a portion of the volatilematerial contact surface of the microporous sheet. The glass doors ofthe fume hood were pulled down, and the air flow through the hood wasadjusted so as to have eight (8) turns (or turnovers) of hood volume perhour. Unless otherwise indicated, the temperature in the hood wasmaintained at 25° C.±5° C. The humidity within in the fume hood wasambient. The test reservoirs were regularly weighed in the hood. Thecalculated weight loss of benzyl acetate, in combination with theelapsed time and surface area of the microporous sheet exposed to theinterior of the test reservoir, were used to determine the volatiletransfer rate of the microporous sheet, in units of mg/(hour*cm²).

As used herein and in the claims, the percent increase in volatilematerial transfer rate of the microporous material of the presentinvention from 25° C. to 60° C. was determined for separate butsubstantially equivalent microporous material sheet samples at 25° C.and 60° C., in accordance with the method described above. Reservoirswere placed in a large glass bell jar and over a 50% aqueous solution ofpotassium chloride also contained in the bell jar. The entire bell jarwith contents was placed in an oven heated to 60° C. The reservoirs wereheld under these conditions for a period of 7 to 10 hours. Thereservoirs were then returned to the hood at ambient conditionsovernight and the process was repeated over several days. Each of thereservoirs was weighed before being placed in the bell jar and afterbeing removed from the bell jar. Upon removal from the bell jar, theweight of each reservoir was taken after the reservoir had returned toambient temperature.

As used herein and in the claims, whether the vapor release surface ofthe microporous material is “substantially free of volatile material inliquid form” was determined in accordance with the followingdescription. When the test reservoirs were weighed, as described above,the vapor release surface of the microporous sheet was examined visuallyby naked eye to determine if drops and/or a film of liquid were presentthere-on. If any evidence of drops (i.e., a single drop) and/or a filmof liquid was visually observed on the vapor release surface, but didnot run off the surface, the microporous sheet was considered to beacceptable. If the drops ran off the surface, the microporous sheet wasdetermined to have failed. If no evidence of drops (i.e., not one drop)and/or a film of liquid was visually observed on the vapor releasesurface, the microporous sheet was determined to be substantially freeof volatile material in liquid form.

Unless otherwise indicated, all ranges disclosed herein are to beunderstood to encompass any and all subranges subsumed therein. Forexample, a stated range of “1 to 10” should be considered to include anyand all subranges between (and inclusive of) the minimum value of 1 andthe maximum value of 10; that is, all subranges beginning with a minimumvalue of 1 or more and ending with a maximum value of 10 or less, e.g.,1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

Unless otherwise indicated, all numbers or expressions, such as thoseexpressing structural dimensions, quantities of ingredients, etc., asused in the specification and claims are understood as modified in allinstances by the term “about.”

The term “volatile material” as used herein and in the claims means amaterial that is capable of conversion to a gaseous or vapor form (i.e.,capable of vaporizing) at ambient room temperature and pressure, in theabsence of imparted additional or supplementary energy (e.g., in theform of heat and/or agitation). The volatile material can comprise anorganic volatile material, which can include those volatile materialscomprising a solvent-based material, or those which are dispersed in asolvent-based material. The volatile material may be in a liquid formand/or in a solid form, and may be naturally occurring or syntheticallyformed. When in a solid form, the volatile material typically sublimesfrom solid form to vapor form, in the absence of an intermediate liquidform. The volatile material may optionally be combined or formulatedwith nonvolatile materials, such as a carrier (e.g., water and/ornonvolatile solvents). In the case of a solid volatile material, thenonvolatile carrier may be in the form of a porous material (e.g., aporous inorganic material) in which the solid volatile material is held.Also, the solid volatile material may be in the form of a semi-solidgel.

The volatile material may be a fragrance material, such as a naturallyoccurring or synthetic perfume oil. Examples of perfume oils from whichthe liquid volatile material may be selected include, but are notlimited to, oil of bergamot, bitter orange, lemon, mandarin, caraway,cedar leaf, clove leaf, cedar wood, geranium, lavender, orange,origanum, petitgrain, white cedar, patchouli, neroili, rose absolute,and combinations thereof. Examples of solid fragrance materials fromwhich the volatile material may be selected include, but are not limitedto, vanillin, ethyl vanillin, coumarin, tonalid, calone, heliotropene,musk xylol, cedrol, musk ketone benzophenone, raspberry ketone, methylnaphthyl ketone beta, phenyl ethyl salicylate, veltol, maltol, maplelactone, proeugenol acetate, evemyl, and combinations thereof.

The volatile material transfer rate of the microporous material can beless than or equal to 0.7 mg/(hour*cm²), or less than or equal to 0.6mg/(hour*cm²), or less than or equal to 0.55 mg/(hour*cm²), or less thanor equal to 0.50 mg/(hour*cm²). The volatile material transfer rate ofthe microporous material can be equal to or greater than 0.02mg/(hour*cm²), or equal to or greater than 0.04 mg/(hour*cm²), or equalto or greater than 0.30 mg/(hour*cm²), or equal to or greater than 0.35mg/(hour*cm²). The volatile material transfer rate of the microporousmaterial may range between any combination of these upper and lowervalues. For example, the volatile material transfer rate of themicroporous material can be from 0.04 to 0.6 mg/(hour*cm²), or from 0.2to 0.6 mg/(hour*cm²), or from 0.30 to 0.55 mg/(hour*cm²), or from 0.35to 0.50 mg/(hour*cm²), in each case inclusive of the recited values.

While not intending to be bound by any theory, when volatile material istransferred from the volatile material contact surface to the vaporrelease surface of the microporous material, it is believed that thevolatile material is in a form selected from liquid, vapor, and acombination thereof. In addition, and without intending to be bound byany theory, it is believed that the volatile material, at least in part,moves through the network of interconnecting pores that communicatesubstantially throughout the microporous material.

The microporous material can have a density of at least 0.7 g/cm³, or atleast 0.8 g/cm³. As used herein and in the claims, the density of themicroporous material is determined by measuring the weight and volume ofa sample of the microporous material. The upper limit of the density ofthe microporous material may range widely, provided it has a targetedvolatile material transfer rate of, for example, from 0.04 to 0.6mg/(hour*cm²), and the vapor release surface is substantially free ofvolatile material in liquid form when volatile material is transferredfrom the volatile material contact surface to said vapor releasesurface. Typically, the density of the microporous material is less thanor equal to 1.5 g/cm³, or less than or equal to 1.0 g/cm³. The densityof the microporous material can range between any of the above-statedvalues, inclusive of the recited values. For example, the microporousmaterial can have a density of from 0.7 g/cm³ to 1.5 g/cm³, such as,from 0.8 g/cm³ to 1.2 g/cm³, inclusive of the recited values.

When the microporous material has a density of at least 0.7 g/cm³, suchas at least 0.8 g/cm³, the volatile material contact surface and thevapor release surface of the microporous material each may be free of acoating material thereon. When free of a coating material thereon, thevolatile material contact surface and the vapor release surface each aredefined by the microporous material.

When the microporous material has a density of at least 0.7% g/cm³, suchas at least 0.8 g/cm³, at least a portion of the volatile materialcontact surface of the microporous material optionally may have a firstcoating thereon, and/or at least a portion of the vapor release surfaceof the microporous material optionally may have a second coatingthereon. The first coating and the second coating may be the same ordifferent. When at least a portion of the volatile material contactsurface has a first coating thereon, the volatile material contactsurface is defined at least in part by the first coating. When at leasta portion of the vapor release surface has a second coating thereon, thevapor release surface is defined at least in part by the second coating.

The first coating and the second coating may each be formed from acoating selected from liquid coatings and solid particulate coatings(e.g., powder coatings). Typically, the first and second coatings eachindependently are formed from a coating selected from liquid coatingswhich may optionally include a solvent selected from water, organicsolvents and combinations thereof. The first and second coatings eachindependently may be selected from crosslinkable coatings (e.g.,thermosetting coatings and photo-curable coatings), andnon-crosslinkable coatings (e.g., air-dry coatings). The first andsecond coatings may be applied to the respective surfaces of themicroporous material in accordance with art-recognized methods, such asspray application, curtain coating, dip coating, and/or drawn-downcoating (e.g., by means of a doctor blade or draw-down bar) techniques.

The first and second coating compositions each independently can includeart-recognized additives, such as antioxidants, ultraviolet lightstabilizers, flow control agents, dispersion stabilizers (e.g., in thecase of aqueous dispersions), and colorants (e.g., dyes and/orpigments). Typically, the first and second coating compositions are freeof colorants, and as such are substantially clear or opaque. Optionaladditives may be present in the coating compositions in individualamounts of from, for example, 0.01 to 10 percent by weight, based on thetotal weight of the coating composition.

The first coating and said second coating each independently can beformed from an aqueous coating composition that includes dispersedorganic polymeric material. The aqueous coating composition may have aparticle size of from 200 to 400 nm. The solids of the aqueous coatingcomposition may vary widely, for example from 0.1 to 30 percent byweight, or from 1 to 20 percent by weight, in each case based on totalweight of the aqueous coating composition. The organic polymerscomprising the aqueous coating compositions may have number averagemolecular weights (Mn) of, for example, from 1000 to 4,000,000, or from10,000 to 2,000,000.

The aqueous coating composition can be selected from aqueouspoly(meth)acrylate dispersions, aqueous polyurethane dispersions,aqueous silicone (or silicon) oil dispersions, and combinations thereof.The poly(meth)acrylate polymers of the aqueous poly(meth)acrylatedispersions may be prepared in accordance with art-recognized methods.For example, the poly(meth)acrylate polymers may include residues (ormonomer units) of alkyl (meth)acrylates having from 1 to 20 carbon atomsin the alkyl group. Examples of alkyl (meth)acrylates having from 1 to20 carbon atoms in the alkyl group include, but are not limited to,methyl (meth)acrylate, ethyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate, propyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate,tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl(meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, and3,3,5-trimethylcyclohexyl (meth)acrylate. For purposes of non-limitingillustration, an example of an aqueous poly(meth)acrylate dispersionfrom which the first and second coating compositions may each beindependently selected is HYCAR 26138, which is commercially availablefrom Lubrizol Advanced Materials, Inc.

The polyurethane polymers of the aqueous polyurethane dispersions, fromwhich the first and second coatings each independently may be selected,include any of those known to the skilled artisan. Typically thepolyurethane polymers are prepared from isocyanate functional materialshaving two or more isocyanate groups, and active hydrogen functionalmaterials having two or more active hydrogen groups. The active hydrogengroups may be selected from, for example, hydroxyl groups, thiol groups,primary amines, secondary amines, and combinations thereof. For purposesof non-limiting illustration, an example of an aqueous polyurethanedispersion from which the first and second coating compositions may eachbe independently selected is WITCOBOND W-240, which is commerciallyavailable from Chemtura Corporation.

The silicon polymers of the aqueous silicone oil dispersions may beselected from known and art-recognized aqueous silicone oil dispersions.For purposes of non-limiting illustration, an example of an aqueoussilicon dispersion from which the first and second coating compositionsmay each be independently selected is MOMENTIVE LE-410, which iscommercially available from Momentive Performance Materials.

The first coating and the second coating each independently can beapplied at any suitable thickness, provided the microporous material hasa targeted volatile material transfer rate of, for example, from 0.04 to0.6 mg/(hour*cm²), and the vapor release surface is substantially freeof volatile material in liquid form when volatile material istransferred from the volatile material contact surface to said vaporrelease surface. Also, the first coating and the second coating eachindependently can have a coating weight (i.e., weight of the coatingwhich is on the microporous material) of from 0.01 to 5.5 g/m², such asfrom 0.1 to 5.0 g/m², or from 0.5 to 3 g/m², or from 0.75 to 2.5 g/m²,or from 1 to 2 g/m².

The microporous material can have a density of less than 0.8 g/cm³, andat least a portion of the volatile material contact surface of themicroporous material can have a first coating thereon, and/or at least aportion of the vapor release surface of the microporous material canhave a second coating thereon. The first coating and the second coatingmay be the same or different, and are each independently as describedpreviously herein with regard to the optional first and second coatingsof the microporous material having a density of at least 0.8 g/cm³.

When less than 0.8 g/cm³, the density of the microporous material of thepresent invention may have any suitable lower limit, provided themicroporous material has a targeted volatile material transfer rate of,for example, from 0.04 to 0.6 mg/(hour*cm²), and the vapor releasesurface is substantially free of volatile material in liquid form whenvolatile material is transferred from the volatile material contactsurface to said vapor release surface. With this particular embodimentof the present invention, the density of the microporous material may befrom 0.6 to less than 0.8 g/cm³, or from 0.6 to 0.75 g/cm³ (e.g., from0.60 to 0.75 g/cm³) or from 0.6 to 0.7 g/cm³ (e.g., from 0.60 to 0.70g/cm³), or from 0.65 to 0.70 g/cm³.

Further, at least a portion of the volatile material contact surface ofthe microporous material can have a first coating thereon, and/or atleast a portion of the vapor release surface of the microporous materialcan have a second coating thereon, in which the first and secondcoatings each independently are selected from a coating compositioncomprising a poly(vinyl alcohol).

With the poly(vinyl alcohol) coated embodiment of the present invention,when the microporous material (i.e., the poly(vinyl alcohol) coatedmicroporous material) is exposed to a temperature increase of from 25°C. to 60° C., the volatile material transfer rate thereof increases byless than or equal 150 percent. When the poly(vinyl alcohol) coatedmicroporous material) is exposed to a temperature increase (e.g., froman ambient temperature of from 25° C. to 60° C.) the volatile materialtransfer rate typically increases, and typically does not decreaseunless, for example, the microporous material has been damaged byexposure to the higher ambient temperature. As such, and as used hereinand in the claims, the statement “the volatile material transfer ratethereof increases by less than or equal to [a stated] percent” (e.g.,150 percent), is inclusive of a lower limit of 0 percent, but is notinclusive of a lower limit that is less than 0 percent.

For purposes of illustration, when the poly(vinyl alcohol) coatedmicroporous material has a volatile material transfer rate of 0.3mg/(hour*cm²) at 25° C., when the microporous material is exposed to atemperature of 60° C., the volatile material transfer rate increases toa value that is less than or equal to 0.75 mg/(hour*cm²).

In an embodiment, when the microporous material (i.e., the poly(vinylalcohol) coated microporous material) is exposed to a temperatureincrease of from 25° C. to 60° C., the volatile material transfer ratethereof increases by less than or equal 125 percent. For example, whenthe poly(vinyl alcohol) coated microporous material has a volatilematerial transfer rate of 0.3 mg/(hour*cm²) at 25° C., when themicroporous material is exposed to a temperature of 60° C., the volatilematerial transfer rate increases to a value that is less than or equalto 0.68 mg/(hour*cm²).

Further, when the microporous material (i.e., the poly(vinyl alcohol)coated microporous material) is exposed to a temperature increase offrom 25° C. to 60° C., the volatile material transfer rate thereofincreases by less than or equal 100 percent. For example, when thepoly(vinyl alcohol) coated microporous material has a volatile materialtransfer rate of 0.3 mg/(hour*cm²) at 25° C., when the microporousmaterial is exposed to a temperature of 60° C., the volatile materialtransfer rate increases to a value that is less than or equal to 0.6mg/(hour*cm²).

The first and second poly(vinyl alcohol) coatings may each beindependently present in any suitable coating weight, provided themicroporous material has a targeted volatile material transfer rate of,for example, at least 0.04 mg/(hour*cm²), and when the microporousmaterial (i.e., the poly(vinyl alcohol) coated microporous material) isexposed to a temperature increase of from 25° C. to 60° C., the volatilematerial transfer rate thereof increases by less than or equal to 150percent. Typically, the first poly(vinyl alcohol) coating and the secondpoly(vinyl alcohol) coating each independently have a coating weight offrom 0.01 to 5.5 g/m², or from 0.1 to 4.0 g/m², or from 0.5 to 3.0 g/m²,or from 0.75 to 2.0 g/m².

The volatile material transfer rate of the poly(vinyl alcohol) coatedmicroporous material can be at least 0.02 mg/(hour*cm²). The volatilematerial transfer rate of the poly(vinyl alcohol) coated microporousmaterial may be equal to or greater than 0.04 mg/(hour*cm²), or equal toor greater than 0.1 mg/(hour*cm²), or equal to or greater than 0.2mg/(hour*cm²), equal to or greater than 0.30 mg/(hour*cm²), or equal toor greater than 0.35 mg/(hour*cm²). The volatile material transfer rateof the poly(vinyl alcohol) coated microporous material may be less thanor equal to 0.7 mg/(hour*cm²), or less than or equal to 0.6mg/(hour*cm²), or less than or equal to 0.55 mg/(hour*cm²), or less thanor equal to 0.50 mg/(hour*cm²). The volatile material transfer rate ofthe poly(vinyl alcohol) coated microporous material may range betweenany combination of these upper and lower values, inclusive of therecited values. For example, the volatile material transfer rate of thepoly(vinyl alcohol) coated microporous material can be at least 0.02mg/(hour*cm²), such as from 0.04 to 0.70 mg/(hour*cm²), or from 0.04 to0.60 mg/(hour*cm²), or from 0.20 to 0.60 mg/(hour*cm²), or from 0.30 to0.55 mg/(hour*cm²), or from 0.35 to 0.50 mg/(hour*cm²), in each caseinclusive of the recited values.

The density of the microporous material of the poly(vinyl alcohol)coated microporous material embodiment of the present invention may varywidely, provided that the poly(vinyl alcohol) coated microporousmaterial has a targeted volatile material transfer rate, for example, atleast 0.04 mg/(hour*cm²), and when the microporous material (i.e., thepoly(vinyl alcohol) coated microporous material) is exposed to atemperature increase of from 25° C. to 60° C., the volatile materialtransfer rate thereof increases by less than or equal to 150 percent.

Further, the density of the microporous material, of the poly(vinylalcohol) coated microporous material, may be at least 0.7 g/cm³, such asat least 0.8 g/cm³ (e.g., from 0.8 to 1.2 g/cm³) all inclusive of therecited values. In an embodiment of the present invention, the densityof the poly(vinyl alcohol) coated microporous material (i.e., thedensity of the microporous material prior to application of thepoly(vinyl alcohol) coating) is less than 0.8 g/cm³. For example, thedensity of the microporous material, of the poly(vinyl alcohol) coatedmicroporous material, may be from 0.6 to less than 0.8 g/cm³, or from0.6 to 0.75 g/cm³ (e.g., from 0.60 to 0.75 g/cm³) or from 0.6 to 0.7g/cm³ (e.g., from 0.60 to 0.70 g/cm³), or from 0.65 to 0.70 g/cm³, allinclusive of the recited values.

With the poly(vinyl alcohol) coated microporous material of the presentinvention, when volatile material is transferred from the volatilematerial contact surface to the vapor release surface, the vapor releasesurface is substantially free of volatile material in liquid form.

The poly(vinyl alcohol) coating may be selected from liquid coatingswhich may optionally include a solvent selected from water, organicsolvents and combinations thereof. The poly(vinyl alcohol) coating maybe selected from crosslinkable coatings (e.g., thermosetting coatings),and non-crosslinkable coatings (e.g., air-dry coatings). The poly(vinylalcohol) coating may be applied to the respective surfaces of themicroporous material in accordance with art-recognized methods, such asspray application, curtain coating, or drawn-down coating (e.g., bymeans of a doctor blade or draw-down bar).

In an embodiment, the first and second poly(vinyl alcohol) coatings areeach independently formed from aqueous poly(vinyl alcohol) coatingcompositions. The solids of the aqueous poly(vinyl alcohol) coatingcomposition may vary widely, for example from 0.1 to 15 percent byweight, or from 0.5 to 9 percent by weight, in each case based on totalweight of the aqueous coating composition. The poly(vinyl alcohol)polymer of the poly(vinyl alcohol) coating compositions may have numberaverage molecular weights (Mn) of, for example, from 100 to 1,000,000,or from 1000 to 750,000.

The poly(vinyl alcohol) polymer of the poly(vinyl alcohol) coatingcomposition may be a homopolymer or copolymer. Comonomer from which thepoly(vinyl alcohol) copolymer may be prepared include those which arecopolymerizable (by means of radical polymerization) with vinyl acetate,and which are known to the skilled artisan. For purposes ofillustration, comonomers from which the poly(vinyl alcohol) copolymermay be prepared include, but are not limited to: (meth)acrylic acid,maleic acid, fumaric acid, crotonic acid, metal salts thereof, alkylesters thereof (e.g., C₂-C₁₀ alkyl esters thereof), polyethylene glycolesters thereof, and polypropylene glycol esters thereof; vinyl chloride;tetrafluoroethylene; 2-acrylamido-2-methyl-propane sulfonic acid and itssalts; acrylamide; N-alkyl acrylamide; N,N-dialkyl substitutedacrylamides; and N-vinyl formamide.

For purposes of non-limiting illustration, an example of poly(vinylalcohol) coating composition that may be used to form the poly(vinylalcohol) coated microporous material of the present invention, is CELVOL325, which is commercially available from Sekisui Specialty Chemicals.

The first and second poly(vinyl alcohol) coating compositions may eachindependently include art-recognized additives, such as antioxidants,ultraviolet light stabilizers, flow control agents, dispersionstabilizers (e.g., in the case of aqueous dispersions), and colorants(e.g., dyes and/or pigments). Typically, the first and second poly(vinylalcohol) coating compositions are free of colorants, and are as suchsubstantially clear or opaque. Optional additives may be present in thepoly(vinyl alcohol) coating compositions in individual amounts of from,for example, 0.01 to 10 percent by weight, based on the total weight ofthe coating composition.

The matrix of the microporous material is composed of substantiallywater-insoluble thermoplastic organic polymer. The numbers and kinds ofsuch polymers suitable for use as the matrix are large. In general, anysubstantially water-insoluble thermoplastic organic polymer which can beextruded, calendered, pressed, or rolled into film, sheet, strip, or webmay be used. The polymer may be a single polymer or it may be a mixtureof polymers. The polymers may be homopolymers, copolymers, randomcopolymers, block copolymers, graft copolymers, atactic polymers,isotactic polymers, syndiotactic polymers, linear polymers, or branchedpolymers. When mixtures of polymers are used, the mixture may behomogeneous or it may comprise two or more polymeric phases.

Examples of classes of suitable substantially water-insolublethermoplastic organic polymers include thermoplastic polyolefins,poly(halo-substituted olefins), polyesters, polyamides, polyurethanes,polyureas, poly(vinyl halides), poly(vinylidene halides), polystyrenes,poly(vinyl esters), polycarbonates, polyethers, polysulfides,polyimides, polysilanes, polysiloxanes, polycaprolactones,polyacrylates, and polymethacrylates. Hybrid classes, from which thewater-insoluble thermoplastic organic polymers may be selected include,for example, thermoplastic poly(urethane-ureas), poly(ester-amides),poly(silane-siloxanes), and poly(ether-esters) are within contemplation.Further examples of suitable substantially water-insoluble thermoplasticorganic polymers include thermoplastic high density polyethylene, lowdensity polyethylene, ultrahigh molecular weight polyethylene,polypropylene (atactic, isotactic, or syndiotactic), poly(vinylchloride), polytetrafluoroethylene, copolymers of ethylene and acrylicacid, copolymers of ethylene and methacrylic acid, poly(vinylidenechloride), copolymers of vinylidene chloride and vinyl acetate,copolymers of vinylidene chloride and vinyl chloride, copolymers ofethylene and propylene, copolymers of ethylene and butene, poly(vinylacetate), polystyrene, poly(omega-aminoundecanoic acid)poly(hexamethylene adipamide), poly(epsilon-caprolactam), andpoly(methyl methacrylate). The recitation of these classes and exampleof substantially water-insoluble thermoplastic organic polymers is notexhaustive, and are provided for purposes of illustration.

Substantially water-insoluble thermoplastic organic polymers may inparticular include, for example, poly(vinyl chloride), copolymers ofvinyl chloride, or mixtures thereof. In an embodiment thewater-insoluble thermoplastic organic polymer includes an ultrahighmolecular weight polyolefin selected from: ultrahigh molecular weightpolyolefin (e.g., essentially linear ultrahigh molecular weightpolyolefin) having an intrinsic viscosity of at least 10deciliters/gram; or ultrahigh molecular weight polypropylene (e.g.,essentially linear ultrahigh molecular weight polypropylene) having anintrinsic viscosity of at least 6 deciliters/gram; or a mixture thereof.In a particular embodiment, the water-insoluble thermoplastic organicpolymer includes ultrahigh molecular weight polyethylene (e.g., linearultrahigh molecular weight polyethylene) having an intrinsic viscosityof at least 18 deciliters/gram.

Ultrahigh molecular weight polyethylene (UHMWPE) is not a thermosetpolymer having an infinite molecular weight, it is technicallyclassified as a thermoplastic. However, because the molecules aresubstantially very long chains, UHMWPE softens when heated but does notflow as a molten liquid in a normal thermoplastic manner. The very longchains and the peculiar properties they provide to UHMWPE are believedto contribute in large measure to the desirable properties ofmicroporous materials made using this polymer.

As indicated earlier, the intrinsic viscosity of the UHMWPE is at leastabout 10 deciliters/gram. Usually the intrinsic viscosity is at leastabout 14 deciliters/gram. Often the intrinsic viscosity is at leastabout 18 deciliters/gram. In many cases the intrinsic viscosity is atleast about 19 deciliters/gram. Although there is no particularrestriction on the upper limit of the intrinsic viscosity, the intrinsicviscosity is frequently in the range of from about 10 to about 39deciliters/gram. The intrinsic viscosity is often in the range of fromabout 14 to about 39 deciliters/gram. In most cases the intrinsicviscosity is in the range of from about 18 to about 39 deciliters/gram.An intrinsic viscosity in the range of from about 18 to about 32deciliters/gram is preferred.

The nominal molecular weight of UHMWPE is empirically related to theintrinsic viscosity of the polymer according to the equation:

M(UHMWPE)=5.3×10⁴[η]^(1.37)

where M(UHMWPE) is the nominal molecular weight and [η] is the intrinsicviscosity of the UHMW polyethylene expressed in deciliters/gram.

As used herein and in the claims, intrinsic viscosity is determined byextrapolating to zero concentration the reduced viscosities or theinherent viscosities of several dilute solutions of the UHMWPE where thesolvent is freshly distilled decahydronaphthalene to which 0.2 percentby weight, 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid,neopentanetetrayl ester [CAS Registry No. 6683-19-8] has been added. Thereduced viscosities or the inherent viscosities of the UHMWPE areascertained from relative viscosities obtained at 135 degree. C. usingan Ubbelohde No. 1 viscometer in accordance with the general proceduresof ASTM D 4020-81, except that several dilute solutions of differingconcentration are employed. ASTM D 4020-81 is, in its entirety,incorporated herein by reference.

In an embodiment, the matrix comprises a mixture of substantially linearultrahigh molecular weight polyethylene having an intrinsic viscosity ofat least 10 deciliters/gram, and lower molecular weight polyethylenehaving an ASTM D 1238-86 Condition E melt index of less than 50 grams/10minutes and an ASTM D 1238-86 Condition F melt index of at least 0.1gram/10 minutes. The nominal molecular weight of the lower molecularweight polyethylene (LMWPE) is lower than that of the UHMW polyethylene.LMWPE is thermoplastic and many different types are known. One method ofclassification is by density, expressed in grams/cubic centimeter androunded to the nearest thousandth, in accordance with ASTM D 1248-84(re-approved 1989), as summarized as follows:

Type Abbreviation Density (g/cm³) Low Density Polyethylene LDPE0.910-0.925 Medium Density Polyethylene MDPE 0.926-0.940 High DensityPolyethylene HDPE 0.941-0.965Any or all of these polyethylenes may be used as the LMWPE in thepresent invention. For some applications, HDPE, may be used because itordinarily tends to be more linear than MDPE or LDPE. ASTM D 1248-84(Reapproved 1989) is, in its entirety, incorporated herein by reference.

Processes for making the various LMWPE's are well known and welldocumented. They include the high pressure process, the PhillipsPetroleum Company process, the Standard Oil Company (Indiana) process,and the Ziegler process.

The ASTM D 1238-86 Condition E (that is, 190 degree. C. and 2.16kilogram load) melt index of the LMWPE is less than about 50 grams/10minutes. Often the Condition E melt index is less than about 25 grams/10minutes. Preferably the Condition E melt index is less than about 15grams/10 minutes.

The ASTM D 1238-86 Condition F (that is, 190 degree. C. and 21.6kilogram load) melt index of the LMWPE is at least 0.1 gram/10 minutes.In many cases the Condition F melt index is at least about 0.5 grain/10minutes. Preferably the Condition F melt index is at least about 1.0gram/10 minutes.

ASTM D 1238-86 is, in its entirety, incorporated herein by reference.

Sufficient UHMWPE and LMWPE should be present in the matrix to providetheir properties to the microporous material. Other thermoplasticorganic polymer may also be present in the matrix so long as itspresence does not materially affect the properties of the microporousmaterial in an adverse manner. The other thermoplastic polymer may beone other thermoplastic polymer or it may be more than one otherthermoplastic polymer. The amount of the other thermoplastic polymerwhich may be present depends upon the nature of such polymer. Examplesof thermoplastic organic polymers which may optionally be presentinclude poly(tetrafluoroethylene), polypropylene, copolymers of ethyleneand propylene, copolymers of ethylene and acrylic acid, and copolymersof ethylene and methacrylic acid. If desired, all or a portion of thecarboxyl groups of carboxyl-containing copolymers may be neutralizedwith sodium, zinc, or the like.

In most cases the UHMWPE and the LMWPE together constitute at leastabout 65 percent by weight of the polymer of the matrix. Often theUHMWPE and the LMWPE together constitute at least about 85 percent byweight of the polymer of the matrix. Preferably the other thermoplasticorganic polymer is substantially absent so that the UHMWPE and the LMWPEtogether constitute substantially 100 percent by weight of the polymerof the matrix.

The UHMWPE can constitute at least one percent by weight of the polymerof the matrix, and the UHMWPE and the LMWPE together constitutesubstantially 100 percent by weight of the polymer of the matrix.

Where the UHMWPE and the LMWPE together constitute 100 percent by weightof the polymer of the matrix of the microporous material, the UHMWPE canconstitute greater than or equal to 40 percent by weight of the polymerof the matrix, such as greater than or equal to 45 percent by weight, orgreater than or equal to 48 percent by weight, or greater than or equalto 50 percent by weight, or greater than or equal to 55 percent byweight of the polymer of the matrix. Also, the UHMWPE can constituteless than or equal to 99 percent by weight of the polymer of the matrix,such as less than or equal to 80 percent by weight, or less than orequal to 70 percent by weight, or less than or equal to 65 percent byweight, or less than or equal to 60 percent by weight of the polymer ofthe matrix. The level of UHMWPE comprising the polymer of the matrix canrange between any of these values inclusive of the recited values.

Likewise, where the UHMWPE and the LMWPE together constitute 100 percentby weight of the polymer of the matrix of the microporous material, theLMWPE can constitute greater than or equal to 1 percent by weight of thepolymer of the matrix, such as greater than or equal to 5 percent byweight, or greater than or equal to 10 percent by weight, or greaterthan or equal to 15 percent by weight, or greater than or equal to 20percent by weight, or greater than or equal to 25 percent by weight, orgreater than or equal to 30 percent by weight, or greater than or equalto 35 percent by weight, or greater than or equal to 40 percent byweight, or greater than or equal to 45 percent by weight, or greaterthan or equal to 50 percent by weight, or greater than or equal to 55percent by weight of the polymer of the matrix. Also, the LMWPE canconstitute less than or equal to 70 percent by weight of the polymer ofthe matrix, such as less than or equal to 65 percent by weight, or lessthan or equal to 60 percent by weight, or less than or equal to 55percent by weight, or less than or equal to 50 percent by weight, orless than or equal to 45 percent by weight of the polymer of the matrix.The level of the LMWPE can range between any of these values inclusiveof the recited values.

It should be noted that for any of the previously described microporousmaterials of the present invention, the LMWPE can comprise high densitypolyethylene.

The microporous material also includes a finely-divided, substantiallywater-insoluble particulate filler material. The particulate fillermaterial may include an organic particulate material and/or an inorganicparticulate material. The particulate filler material typically is notcolored, for example, the particulate filler material is a white oroff-white particulate filler material, such as a siliceous or clayparticulate material.

The finely divided substantially water-insoluble filler particles mayconstitute from 20 to 90 percent by weight of the microporous material.For example, such filler particles may constitute from 20 to 90 percentby weight of the microporous material, such as from 30 percent to 90percent by weight of the microporous material, or from 40 to 90 percentby weight of the microporous material, or from 40 to 85 percent byweight of the microporous material, or from 50 to 90 percent by weightof the microporous material and even from 60 percent to 90 percent byweight of the microporous material.

The finely divided substantially water-insoluble particulate filler maybe in the form of ultimate particles, aggregates of ultimate particles,or a combination of both. At least about 90 percent by weight of thefiller used in preparing the microporous material has gross particlesizes in the range of from 0.5 to about 200 micrometers, such as from 1to 100 micrometers, as determined by the use of a laser diffractionparticle size instrument, LS230 from Beckman Coulton, capable ofmeasuring particle diameters as small as 0.04 micrometers. Typically, atleast 90 percent by weight of the particulate filler has gross particlesizes in the range of from 10 to 30 micrometers. The sizes of the filleragglomerates may be reduced during processing of the ingredients used toprepare the microporous material. Accordingly, the distribution of grossparticle sizes in the microporous material may be smaller than in theraw filler itself.

Non-limiting examples of suitable organic and inorganic particulatematerials, that may be used in the microporous material of the presentinvention, include those described in U.S. Pat. No. 6,387,519 B1 atcolumn 9, line 4 to column 13, line 62, the cited portions of which areincorporated herein by reference.

In a particular embodiment of the present invention, the particulatefiller material comprises siliceous materials. Non-limiting examples ofsiliceous fillers that may be used to prepare the microporous materialinclude silica, mica, montmorillonite, kaolinite, nanoclays such ascloisite available from Southern Clay Products, talc, diatomaceousearth, vermiculite, natural and synthetic zeolites, calcium silicate,aluminum silicate, sodium aluminum silicate, aluminum polysilicate,alumina silica gels and glass particles. In addition to the siliceousfillers, other finely divided particulate substantially water-insolublefillers optionally may also be employed. Non-limiting examples of suchoptional particulate fillers include carbon black, charcoal, graphite,titanium oxide, iron oxide, copper oxide, zinc oxide, antimony oxide,zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide, bariumsulfate, strontium sulfate, calcium carbonate, and magnesium carbonate.In a non-limiting embodiment, the siliceous filler may include silicaand any of the aforementioned clays. Non-limiting examples of silicasinclude precipitated silica, silica gel, fumed silica, and combinationsthereof.

Silica gel is generally produced commercially by acidifying an aqueoussolution of a soluble metal silicate, e.g., sodium silicate at low pHwith acid. The acid employed is generally a strong mineral acid such assulfuric acid or hydrochloric acid, although carbon dioxide can be used.Inasmuch as there is essentially no difference in density between thegel phase and the surrounding liquid phase while the viscosity is low,the gel phase does not settle out, that is to say, it does notprecipitate. Consequently, silica gel may be described as anon-precipitated, coherent, rigid, three-dimensional network ofcontiguous particles of colloidal amorphous silica. The state ofsubdivision ranges from large, solid masses to submicroscopic particles,and the degree of hydration from almost anhydrous silica to softgelatinous masses containing on the order of 100 parts of water per partof silica by weight.

Precipitated silica generally is produced commercially by combining anaqueous solution of a soluble metal silicate, ordinarily alkali metalsilicate such as sodium silicate, and an acid so that colloidalparticles of silica will grow in a weakly alkaline solution and becoagulated by the alkali metal ions of the resulting soluble alkalimetal salt. Various acids may be used, including but not limited tomineral acids. Non-limiting examples of acids that may be used includehydrochloric acid and sulfuric acid, but carbon dioxide can also be usedto produce precipitated silica. In the absence of a coagulant, silica isnot precipitated from solution at any pH. In a non-limiting embodiment,the coagulant used to effect precipitation of silica may be the solublealkali metal salt produced during formation of the colloidal silicaparticles, or it may be an added electrolyte, such as a solubleinorganic or organic salt, or it may be a combination of both.

Precipitated silicas are available in many grades and forms from PPGIndustries, Inc. These silicas are sold under the Hi-Sil® tradename.

For purposes of the present invention, the finely divided particulatesubstantially water-insoluble siliceous filler can comprise at least 50percent by weight (e.g., at least 65, at least 75 percent by weight), orat least 90 percent by weight of the substantially water-insolublefiller material. The siliceous filler may comprise from 50 to 90 percentby weight (e.g., from 60 to 80 percent by weight) of the particulatefiller material, or the siliceous filler may comprise substantially allof the substantially water-insoluble particulate filler material.

The particulate filler (e.g., the siliceous filler) typically has a highsurface area allowing the filler to carry much of the processingplasticizer composition used to produce the microporous material of thepresent invention. The filler particles are substantiallywater-insoluble and also can be substantially insoluble in any organicprocessing liquid used to prepare the microporous material. This canfacilitate retention of the particulate filler within the microporousmaterial.

The microporous material of the present may also include minor amounts(e.g., less than or equal to 5 percent by weight, based on total weightof the microporous material) of other materials used in processing, suchas lubricant, processing plasticizer, organic extraction liquid, water,and the like. Further materials introduced for particular purposes, suchas thermal, ultraviolet and dimensional stability, may optionally bepresent in the microporous material in small amounts (e.g., less than orequal to 15 percent by weight, based on total weight of the microporousmaterial). Examples of such further materials include, but are notlimited to, antioxidants, ultraviolet light absorbers, reinforcingfibers such as chopped glass fiber strand, and the like. The balance ofthe microporous material, exclusive of filler and any coating, printingink, or impregnant applied for one or more special purposes isessentially the thermoplastic organic polymer.

The microporous material of the present invention, also includes anetwork of interconnecting pores, which communicate substantiallythroughout the microporous material. On a coating-free, printing inkfree and impregnant-free basis, pores typically constitute from 35 to 95percent by volume, based on the total volume of the microporousmaterial, when made by the processes as further described herein. Thepores may constitute from 60 to 75 percent by volume of the microporousmaterial, based on the total volume of the microporous material. As usedherein and in the claims, the porosity (also known as void volume) ofthe microporous material, expressed as percent by volume, is determinedaccording to the following equation:

Porosity=100[1−d ₁ /d ₂]

where, d₁ is the density of the sample, which is determined from thesample weight and the sample volume as ascertained from measurements ofthe sample dimensions; and d₂ is the density of the solid portion of thesample, which is determined from the sample weight and the volume of thesolid portion of the sample. The volume of the solid portion of themicroporous material is determined using a Quantachrome stereopycnometer(Quantachrome Corp.) in accordance with the operating manualaccompanying the instrument.

The volume average diameter of the pores of the microporous material isdetermined by mercury porosimetry using an Autoscan mercury porosimeter(Quantachrome Corp.) in accordance with the operating manualaccompanying the instrument. The volume average pore radius for a singlescan is automatically determined by the porosimeter. In operating theporosimeter, a scan is made in the high pressure range (from 138kilopascals absolute to 227 megapascals absolute). If 2 percent or lessof the total intruded volume occurs at the low end (from 138 to 250kilopascals absolute) of the high pressure range, the volume averagepore diameter is taken as twice the volume average pore radiusdetermined by the porosimeter. Otherwise, an additional scan is made inthe low pressure range (from 7 to 165 kilopascals absolute) and thevolume average pore diameter is calculated according to the equation:

d=2[v ₁ r ₁ /w ₁ +v ₂ r ₂ /w ₂ ]/[v ₁ /w ₁ +v ₂ /w ₂]

where, d is the volume average pore diameter; v₁ is the total volume ofmercury intruded in the high pressure range; v₂ is the total volume ofmercury intruded in the low pressure range; r₁ is the volume averagepore radius determined from the high pressure scan; r₂ is the volumeaverage pore radius determined from the low pressure scan; w₁ is theweight of the sample subjected to the high pressure scan; and w₂ is theweight of the sample subjected to the low pressure scan.

Generally on a coating-free, printing ink-free and impregnant-freebasis, the volume average diameter of the pores of the microporousmaterial is at least 0.02 micrometers, typically at least 0.04micrometers, and more typically at least 0.05 micrometers. On the samebasis, the volume average diameter of the pores of the microporousmaterial is also typically less than or equal to 0.5 micrometers, moretypically less than or equal to 0.3 micrometers, and further typicallyless than or equal to 0.25 micrometers. The volume average diameter ofthe pores, on this basis, may range between any of these values,inclusive of the recited values. For example, the volume averagediameter of the pores of the microporous material may range from 0.02 to0.5 micrometers, or from 0.04 to 0.3 micrometers, or from 0.05 to 0.25micrometers, in each case inclusive of the recited values.

In the course of determining the volume average pore diameter by meansof the above described procedure, the maximum pore radius detected mayalso be determined. This is taken from the low pressure range scan, ifrun; otherwise it is taken from the high pressure range scan. Themaximum pore diameter of the microporous material is typically twice themaximum pore radius.

Coating, printing and impregnation processes can result in filling atleast some of the pores of the microporous material. In addition, suchprocesses may also irreversibly compress the microporous material.Accordingly, the parameters with respect to porosity, volume averagediameter of the pores, and maximum pore diameter are determined for themicroporous material prior to application of one or more of theseprocesses.

Numerous art-recognized processes may be used to produce the microporousmaterials of the present invention. For example, the microporousmaterial of the present invention can be prepared by mixing togetherfiller particles, thermoplastic organic polymer powder, processingplasticizer and minor amounts of lubricant and antioxidant, until asubstantially uniform mixture is obtained. The weight ratio ofparticulate filler to polymer powder employed in forming the mixture isessentially the same as that of the microporous material to be produced.The mixture, together with additional processing plasticizer, istypically introduced into the heated barrel of a screw extruder.Attached to the terminal end of the extruder is a sheeting die. Acontinuous sheet formed by the die is forwarded without drawing to apair of heated calender rolls acting cooperatively to form a continuoussheet of lesser thickness than the continuous sheet exiting from thedie. The level of processing plasticizer present in the continuous sheetat this point in the process can vary widely. For example, the level ofprocessing plasticizer present in the continuous sheet, prior toextraction as described herein below, can be greater than or equal to 30percent by weight of the continuous sheet, such as greater than or equalto 40 percent by weight, or greater than or equal to 45 percent byweight of the continuous sheet prior to extraction. Also, the amount ofprocessing plasticizer present in the continuous sheet prior toextraction can be less than or equal to 70 percent by weight of thecontinuous sheet, such as less than or equal to 65 percent by weight, orless than or equal to 60 percent by weight, or less than or equal to 55percent by weight of the continuous sheet prior to extraction. The levelof processing plasticizer present in the continuous sheet at this pointin the process, prior to extraction, can range between any of thesevalues inclusive of the recited values.

The continuous sheet from the calender is then passed to a firstextraction zone where the processing plasticizer is substantiallyremoved by extraction with an organic liquid, which is a good solventfor the processing plasticizer, a poor solvent for the organic polymer,and more volatile than the processing plasticizer. Usually, but notnecessarily, both the processing plasticizer and the organic extractionliquid are substantially immiscible with water. The continuous sheetthen passes to a second extraction zone where residual organicextraction liquid is substantially removed by steam and/or water. Thecontinuous sheet is then passed through a forced air dryer forsubstantial removal of residual water and remaining residual organicextraction liquid. From the dryer the continuous sheet, which ismicroporous material, is passed to a take-up roll.

The processing plasticizer is a liquid at room temperature and usuallyis a processing oil such as paraffinic oil, naphthenic oil, or aromaticoil. Suitable processing oils include those meeting the requirements ofASTM D 2226-82, Types 103 and 104. More typically, processing oilshaving a pour point of less than 220° C. according to ASTM D 97-66(re-approved 1978), are used to produce the microporous material of thepresent invention. Processing plasticizers useful in preparing themicroporous material of the present invention are discussed in furtherdetail in U.S. Pat. No. 5,326,391 at column 10, lines 26 through 50,which disclosure is incorporated herein by reference.

In an embodiment of the present invention, the processing plasticizercomposition used to prepare the microporous material has littlesolvating effect on the polyolefin at 60° C., and only a moderatesolvating effect at elevated temperatures on the order of 100° C. Theprocessing plasticizer composition generally is a liquid at roomtemperature. Non-limiting examples of processing oils that may be usedcan include SHELLFLEX® 412 oil, SHELLFLEX® 371 oil (Shell Oil Co.),which are solvent refined and hydrotreated oils derived from naphtheniccrude oils, ARCOprime® 400 oil (Atlantic Richfield Co.) and KAYDOL® oil(Witco Corp.), which are white mineral oils. Other non-limiting examplesof processing plasticizers can include phthalate ester plasticizers,such as dibutyl phthalate, bis(2-ethylhexyl) phthalate, diisodecylphthalate, dicyclohexyl phthalate, butyl benzyl phthalate, andditridecyl phthalate. Mixtures of any of the foregoing processingplasticizers can be used to prepare the microporous material of thepresent invention.

There are many organic extraction liquids that can be used to preparethe microporous material of the present invention. Examples of othersuitable organic extraction liquids include those described in U.S. Pat.No. 5,326,391 at column 10, lines 51 through 57, which disclosure isincorporated herein by reference.

The extraction fluid composition can comprise halogenated hydrocarbons,such as chlorinated hydrocarbons and/or fluorinated hydrocarbons. Inparticular, the extraction fluid composition may include halogenatedhydrocarbon(s) and have a calculated solubility parameter coulomb term(δclb) ranging from 4 to 9 (Jcm³)^(1/2). Non-limiting examples ofhalogenated hydrocarbon(s) suitable as the extraction fluid compositionfor use in producing the microporous material of the present inventioncan include one or more azeotropes of halogenated hydrocarbons selectedfrom trans-1,2-dichloroethylene, 1,1,1,2,2,3,4,5,5,5-decafluoropentane,and/or 1,1,1,3,3-pentafluorobutane. Such materials are availablecommercially as VERTREL MCA (a binary azeotrope of1,1,1,2,2,3,4,5,5,5-dihydrodecafluoropentane andtrans-1,2-dichloroethylene: 62%/38%) and VERTREL CCA (a ternaryazeotrope of 1,1,1,2,2,3,4,5,5,5-dihydrodecafluorpentane,1,1,1,3,3-pentafluorbutane, and trans-1,2-dichloroethylene: 33%/28%/39%)both available from MicroCare Corporation.

The residual processing plasticizer content of microporous materialaccording to the present invention is usually less than 10 percent byweight, based on the total weight of the microporous material, and thisamount may be further reduced by additional extractions using the sameor a different organic extraction liquid. Often the residual processingplasticizer content is less than 5 percent by weight, based on the totalweight of the microporous material, and this amount may be furtherreduced by additional extractions.

The microporous material of the present invention may also be producedaccording to the general principles and procedures of U.S. Pat. Nos.2,772,322; 3,696,061; and/or 3,862,030. These principles and proceduresare particularly applicable where the polymer of the matrix is or ispredominately poly(vinyl chloride) or a copolymer containing a largeproportion of polymerized vinyl chloride.

Microporous materials produced by the above-described processesoptionally may be stretched. Stretching of the microporous materialtypically results in both an increase in the void volume of thematerial, and the formation of regions of increased or enhancedmolecular orientation. As is known in the art, many of the physicalproperties of molecularly oriented thermoplastic organic polymer,including tensile strength, tensile modulus, Young's modulus, andothers, differ (e.g., considerably) from those of the correspondingthermoplastic organic polymer having little or no molecular orientation.Stretching is typically accomplished after substantial removal of theprocessing plasticizer as described above.

Various types of stretching apparatus and processes are well known tothose of ordinary skill in the art, and may be used to accomplishstretching of the microporous material of the present invention.Stretching of the microporous materials is described in further detailin U.S. Pat. No. 5,326,391 at column 11, line 45 through column 13, line13, which disclosure is incorporated herein by reference.

The present invention is more particularly described in the examplesthat follow, which are intended to be illustrative only, since numerousmodifications and variations therein will be apparent to those skilledin the art. Unless otherwise specified, all parts and percentages are byweight.

EXAMPLES

In Part 1 of the following examples, the materials and methods used toprepare the Example and Comparative mixes prepared in the pilot plantand presented in Table 1 and the Example mixes prepared in the scale-upprocess and Comparative commercial samples presented in Table 2 aredescribed. In Part 2, the methods used to extrude, calender and extractthe sheets prepared from the mixes of Part 1 and Part 2 are described.In Part 3, the methods used to determine the physical propertiesreported in Tables 3 and 4 are described. In Parts 4A and 4B, thecoating formulations used are listed in Tables 5 and 7 and theproperties of the coated sheets are listed in Tables 6 and 8. In Part 5,The Benzyl Acetate Test results for the products of Tables 1, 2, 6 and 8are listed in Tables 9, 10, 11 and 12.

Part 1 Mix Preparation

The dry ingredients were weighed into a FM-130D Littleford plough blademixer with one high intensity chopper style mixing blade in the orderand amounts (grams (g)) specified in Table I. The dry ingredients werepremixed for 15 seconds using the plough blades only. The process oilwas then pumped in via a hand pump through a spray nozzle at the top ofthe mixer, with only the plough blades running. The pumping time for theexamples varied between 45-60 seconds. The high intensity chopper bladewas turned on, along with the plough blades, and the mix was mixed for30 seconds. The mixer was shut off and the internal sides of the mixerwere scrapped down to insure all ingredients were evenly mixed. Themixer was turned back on with both high intensity chopper and ploughblades turned on, and the mix was mixed for an additional 30 seconds.The mixer was turned off and the mix dumped into a storage container.

TABLE 1 Samples Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 SilicaHiSil 135 (a) 1393 1393 1393 1393 0 0 1814 1814 Silica Inhibisil (b) 0.00.0 0.0 0.0 1816 1816 0.0 0.0 CaCO₃ © 544.3 544.3 544.3 544.3 709.0709.0 0.0 0.0 TiO₂ (d) 90.7 90.7 90.7 90.7 118.0 118.0 87.3 87.3 UHMWPE(e) 515.3 515.3 515.3 515.3 581.0 671.0 592.0 592.0 HDPE (f) 475.4 475.4475.4 475.4 710.0 619.0 129.0 0.0 LDPE (g) 0.0 0.0 0.0 0.0 0.0 0.0 664.5793.5 Antioxidant (h) 14.5 14.5 14.5 14.5 18.9 18.9 20.1 20.1 Lubricant(i) 14.5 14.5 14.5 14.5 18.9 18.9 21.6 21.6 Polypropylene (j) 0.0 0.00.0 0.0 0.0 0.0 0.0 0.0 CFA (k) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 NanoclayMB (l) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Mix oil (m) 2841 2841 2841 2841931 885 2836 2836 Process Oil (%) 47.8% 48.0% 49.8% 52.6% 47.8% 47.2%53.3% 56.0% Samples Ex. 11 CE 1 CE 2 CE 3 CE 4 CE 5 Silica HiSil 135 (a)1814 1393 1393 2270 2270 2270 Silica Inhibisil (b) 0.0 0.0 0.0 0.0 0.00.0 CaCO₃ © 0.0 544.3 544.3 0.0 0.0 0.0 TiO₂ (d) 87.3 90.7 90.7 91.091.0 91.0 UHMWPE (e) 592.0 515.3 515.3 560.0 285.0 654.0 HDPE (f) 0.0475.4 475.4 560.0 654.0 654.0 LDPE (g) 793.5 0.0 0.0 0.0 0.0 0.0Antioxidant (h) 20.1 14.5 14.5 7.7 7.7 7.7 Lubricant (i) 21.6 14.5 14.522.7 22.7 22.7 Polypropylene (j) 0.0 0.0 0.0 185.0 370.0 0.0 CFA (k) 0.00.0 0.0 0.0 0.0 194.7 Nanoclay MB (l) 0.0 0.0 0.0 0.0 0.0 194.7 Mix oil(m) 2836 2841 2841 3655 3851 3850 Process Oil (%) 52.4% 55.9% 57.4%60.5% 59.6% 57.7% (a) HI-SIL ® 135 precipitated silica from PPGIndustries, Inc. (b) INHIBISIL75 precipitated silica from PPGIndustries, Inc. (c) Calcium carbonate from Camel White (d) TIPURE ®R-103 titanium dioxide from E. I. du Pont de Nemours and Company (e)GUR ® 4130 Ultra High Molecular Weight Polyethylene (UHMWPE), fromTicona Corp. (f) FINA ® 1288 High Density Polyethylene (HDPE), fromTotal Petrochemicals (g) Petrothene ® NA206000 LDPE from Lyondell Basel(h) CYANOX ® 1790 antioxidant from Cytec Industries, Inc. (i) Calciumstearate lubricant, technical grade (j) Used was PRO-FAX ® 7523Polypropylene Copolymer from Ashland Distribution. (k) Foam PE MB, achemical foaming agent from Amacet Corporation (l) NanoMax ® HDPEmaterbatach nanoclay from Nanocor (m) Tufflo ® 6056 process oil from PPCLubricants

Scale-up Examples 10-18 were prepared in a plant scale-up batch sizeusing production scale equipment similar to the equipment and proceduresdescribed above. The scale-up samples were prepared from a mix ofingredients listed in Table 2 as the weight percent of the total mix.

TABLE 2 Ingredients Ex. 10 Ex. 11 Ex. 12 Ex 13 Ex. 14 Ex. 15 Ex. 16 Ex.17 Ex. 18 HiSil ® 135 (a) 23.66 23.66 23.66 23.66 24.77 24.77 24.7724.77 24.77 CaCO₃ (c) 9.24 9.24 9.24 9.24 9.68 9.68 9.68 9.68 9.68 TiO₂(d) 1.54 1.54 1.54 1.54 1.61 1.61 1.61 1.61 1.61 UHMWPE (e) 8.75 8.758.75 8.75 9.16 9.16 9.16 8.45 8.45 HDPE (f) 8.07 8.07 8.07 8.07 8.458.45 8.45 9.16 9.16 Antioxidant (h) 0.25 0.25 0.25 0.25 0.26 0.26 0.260.26 0.26 Lubricant (i) 0.25 0.25 0.25 0.25 0.26 0.26 0.26 0.26 0.26 MixOil (m) 48.24 48.24 48.24 48.24 45.81 45.81 45.81 45.81 45.81

Part 2 Extrusion, Calendering and Extraction

The mixes of the Examples 1-9 and Comparative Examples 1-5 were extrudedand calendered into final sheet form using an extrusion system includinga feeding, extrusion and calendering system described as follows. Agravimetric loss in weight feed system (K-tron model #K2MLT35D5) wasused to feed each of the respective mixes into a 27 mm twin screwextruder (model # was Leistritz Micro-27gg). The extruder barrel wascomprised of eight temperature zones and a heated adaptor to the sheetdie. The extrusion mixture feed port was located just prior to the firsttemperature zone. An atmospheric vent was located in the thirdtemperature zone. A vacuum vent was located in the seventh temperaturezone.

The mix was fed into the extruder at a rate of 90 g/minute. Additionalprocessing oil also was injected at the first temperature zone, asrequired, to achieve the desired total oil content in the extrudedsheet. The oil contained in the extruded sheet (extrudate) beingdischarged from the extruder is referenced herein as the “extrudate oilweight percent”.

Extrudate from the barrel was discharged into a 15-centimeter wide sheetMasterflex® die having a 1.5 millimeter discharge opening. The extrusionmelt temperature was 203-210° C. and the throughput was 7.5 kilogramsper hour.

The calendering process was accomplished using a three-roll verticalcalender stack with one nip point and one cooling roll. Each of therolls had a chrome surface. Roll dimensions were approximately 41 cm inlength and 14 cm in diameter. The top roll temperature was maintainedbetween 135° C. to 140° C. The middle roll temperature was maintainedbetween 140° C. to 145° C. The bottom roll was a cooling roll whereinthe temperature was maintained between 10-21° C. The extrudate wascalendered into sheet form and passed over the bottom water cooled rolland wound up.

A sample of sheet cut to a width up to 25.4 cm and length of 305 cm wasrolled up and placed in a canister and exposed to hot liquid1,1,2-trichloroethylene for approximately 7-8 hours to extract oil fromthe sheet sample. Afterwards, the extracted sheet was air dried andsubjected to test methods described hereinafter.

The mixes of the Scale-up Examples 10-18 were extruded and calenderedinto final sheet form using an extrusion system and oil extractionprocess that was a production sized version of the system describedabove, carried out as described in U.S. Pat. No. 5,196,262, at column 7,line 52, to column 8, line 47. The final sheets were tested for physicalparameters using the test methods described above in Part 3. ComparativeExamples 6-10 were commercial microporous products identified asfollows: CE 6 was TESLIN® Digital; CE 7 was TESLIN® SP 10 mil; CE 8 wasTESLIN® SP 14 mil; and CE 9 was TESLIN® SP 12 mil.

Part 3 Testing and Results

Physical properties measured on the extracted and dried films and theresults obtained are listed in Tables 3 and 4. The extrudate oil weightpercent was measured using a Soxhlet extractor. The extrudate oil weightpercent determination used a specimen of extrudate sheet with no priorextraction. A sample specimen approximately 2.25×5 inches (5.72 cm×12.7cm) was weighed and recorded to four decimal places. Each specimen wasthen rolled into a cylinder and placed into a Soxhlet extractionapparatus and extracted for approximately 30 minutes usingtrichloroethylene (TCE) as the solvent. The specimens were then removedand dried. The extracted and dried specimens were then weighed. The oilweight percentage values (extrudate) was calculated as follows:

Oil Wt. %=(initial wt.−extracted wt.)×100/initial wt.

Thickness was determined using an Ono Sokki thickness gauge EG-225. Two4.5×5 inch (11.43 cm×12.7 cm) specimens were cut from each sample andthe thickness for each specimen was measured in nine places (at least ¾of an inch (1.91 cm) from any edge). The arithmetic average of thereadings was recorded in mils to 2 decimal places and converted tomicrons.

The density of the above-described examples was determined by dividingthe average anhydrous weight of two specimens measuring 4.5×5 inches(11.43 cm×12.7 cm) that were cut from each sample by the average volumeof those specimens. The average volume was determined by boiling the twospecimens in deionized water for 10 minutes, removing and placing thetwo specimens in room temperature deionized water, weighing eachspecimen suspended in deionized water after it has equilibrated to roomtemperature and weighing each specimen again in air after the surfacewater was blotted off. The average volume of the specimens wascalculated as follows:

Volume (avg.)=[(weight of lightly blotted specimens weighed in air−sumof immersed weights)×1.002]/2

The anhydrous weight was determined by weighing each of the twospecimens on an analytical balance and multiplying that weight by 0.98since it was assumed that the specimens contained 2 percent moisture.

The Porosity reported in Tables 3 and 4 was determined using a Gurleydensometer, model 4340, manufactured by GPI Gurley Precision Instrumentsof Troy, New York. The Porosity reported was a measure of the rate ofair flow through a sample or it's resistance to an air flow through thesample. The unit of measure is a “Gurley second” and represents the timein seconds to pass 100 cc of air through a 1 inch square area using apressure differential of 4.88 inches of water. Lower values equate toless air flow resistance (more air is allowed to pass freely). Themeasurements were completed using the procedure listed in the manual,MODEL 4340 Automatic Densometer and Smoothness Tester InstructionManual. TAPPI method T 460 om-06-Air Resistance of Paper can also bereferenced for the basic principles of the measurement.

TABLE 3 Property Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 SheetThickness (μm) 262 264 264 262 371 419 173 155 Extrudate Oil wt. % 47.8%48.0% 49.8% 52.6% 47.8% 47.2% 53.5% 56.0% Density (g/cc) 0.764 0.8280.755 0.707 0.892 0.901 0.646 0.612 Porosity (Gurley Sec.) 2148 21612009 1988 1685 1730 3787 3735 Property Ex. 9 CE 1 CE 2 CE 3 CE 4 CE 5Sheet Thickness (μm) 173 260 246 174 160 169 Extrudate Oil wt. % 52.4%55.9% 57.4% 60.5% 59.6% 57.7% Density (g/cc) 0.701 0.750 0.695 0.5840.659 0.620 Porosity (Gurley Sec.) 4155 1842 1517 1473 1309 1410

TABLE 4 Property Ex. 10 Ex. 11 Ex. 12 Ex 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17Sheet Thickness (μm) 291 293 269 286 289 288 278 277 Extrudate Oil wt. %58.0% 57.6% 58.0% 57.1% 55.0% 53.5% 54.0% 54.0% Density (g/cc) 0.7950.804 0.809 0.815 0.818 0.882 0.835 0.835 Porosity (Gurley Sec.) 28773017 3395 3208 2800 2872 3048 2849 Property Ex. 18 CE 6 CE 7 CE 8 CE 9CE 10 Sheet Thickness (μm) 284 284 157 250 359 306 Extrudate Oil wt. %53.0% — — — — — Density (g/cc) 0.862 0.719 0.607 0.677 0.691 0.672Porosity (Gurley Sec.) 3102 5983 1867 3659 4110 4452

Part 4 A Coating Formulations and Coated Products

Coatings 1-5 listed in Table 5 were prepared by dispersing CELVOL® 325polyvinyl alcohol in cool water under mild agitation in a 600 mL beaker.Mild agitation was provided with a 1″ (2.54 cm) paddle stirrer driven byan electric stir motor. The mixture was heated to 190° F. (87.8° C.) andstirred for 20-30 minutes. The resultant solution was allowed to cool toroom temperature while stirring. Specific mix amounts and resultantmeasured solids are outlined in Table 5.

TABLE 5 Coating Formulations CELVOL ® 325, Deionized water, MeasuredSolids, Coating # (grams) (grams) % by weight 1 7.5 292.5 2.5 ± 0.3 211.3 288.7 3.8 ± 0.3 3 13.5 286.5 4.5 ± 0.3 4 18.0 282.0 6.0 ± 0.3 515.0 285.0 5.0 ± 0.3

The coatings, confirmed to be free of visible un-dissolved particles,were applied to TESLIN® HD microporous substrate sold by PPG Industries,Pittsburgh, Pa. The coatings were applied to sheets of 8.5″×11″, (21.59cm×27.94 cm) 11 mils thick substrate each of which had been tare on abalance prior to placing the sheet on a clean glass surface and usingtape to adhere the top corners of the sheet to the glass. A piece ofclear 10 mil thick polyester 11″×3″ (27.94 cm×7.62 cm) was positionedacross the top edge of the sheet, covering ½″ (1.27 cm) down from thetop edge of the sheet. The polyester was fixed to the glass surface withtape. A wire wrapped metering rod from Diversified Enterprises wasplaced 1-2 inches above the sheet, parallel to the top edge, near thetop edge of the polyester. A 10-20 mL quantity of coating was depositedas a bead strip (approximately ¼″ inches (0.64 cm) wide) directly nextto and touching the metering rod using a disposable pipette. The bar wasdrawn completely across the sheet, attempting a continuous/constantrate. The resultant wet sheet was removed from the glass surface,immediately placed on the previously tare balance, weighed, the wetcoating weight recorded then the coated sheet was placed in a forced airoven and dried at 95° C. for 2 minutes. The dried sheet was removed fromthe oven and the same coating procedure was repeated to the same coatedsheet surface. The two wet coating weights were used to calculate thefinal dry coat weight in grams per square meter. The coated sheets ofExamples 19-23 are described in Table 6.

TABLE 6 Final Coated Sheets Coating Wire Wrapped 1^(sl) Wet Coat 2^(nd)Wet Coat Total wet coating Calculated Final Example # Solids, % Rod #Weight, grams Weight, grams weight, grams Coat Weight, gsm 19 2.5 3 0.60.65 1.25 0.5 ± 0.1 20 3.8 3 0.61 0.59 1.20 0.75 ± 0.1  21 4.5 3 0.700.64 1.34 1.0 ± 0.2 22 6 3 0.76 0.64 1.40 1.5 ± 0.1 23 5 10 1.18 1.202.38 2.1 ± 0.2

The following formula was used to calculate the final dry coat weight.

Calculated Final Dry Coat Weight in grams per square meter=((coatingssolids×0.01)×(1^(st) wet coating wgt.+2^(nd) wet coatingwgt.))/(8.5×10.5)×1550

Part 4B Coating Formulations and Coated Products

The procedure of Part 4A was followed in preparing the coatingformulations of Coatings 6-12, except that Coating 7 was mixed for 2days prior to use. The coating formulations are listed in Table 7.

The substrate used in this Part 4B was TESLIN® SP1000 microporoussubstrate sold by PPG Industries, Pittsburgh, Pa. The same procedureused in Part 4A was followed except that some sheets were coated on bothsides, drying the first coated side prior to applying the second on theopposite side and a number 9 metering rod was used for all of thecoatings. Information on the final coated sheets is included in Table 8.

TABLE 7 Coating Formulations with amounts listed in grams Ingredients 67 8 9 10 11 12 Witcobond W240_((n)) 8 8 8 8 16 0 0 Aerosil ® 200_((o))2.5 0 0 0 0 0 0 CaCO_(3(c)) 0 2.5 0 0 0 0 0 HiSil ® T 700_((p)) 0 0 2.50 0 0 0 Lo-Vel ® 6200_((q)) 0 0 0 2.5 0 0 0 MOMENTIVE LE-410_((r)) 0 0 00 0 0.54 0 HYCAR 26138_((s)) 0 0 0 0 0 0 10 Deionized Water 39.5 39.539.5 39.5 34.0 49.5 40 Total, grams 50 50 50 50 50 50 50 Solids, % 10 1010 10 10 0.4 10 _((n))WITCOBOND W-240, an aqueous polyurethanedispersion from Chemtura Corporation. _((o))Aerosil ® 200 fumed silicafrom Degussa. _((p))HiSil ®T700 precipitated silica from PPG Industries,Inc. _((q))Lo-Vel ®6200 precipitated silica from PPG Industries, Inc._((r))MOMENTIVE LE-410 an aqueous silicon dispersion from MomentivePerformance Materials. _((s))HYCAR 26138, an aqueous poly(meth)acrylatedispersion from Lubrizol Advanced Materials, Inc.

TABLE 8 Final Coated Sheets Wet Coating weigh

Final Coatin

Example # Coating # Coating Type (grams weight (gsm

24 10 Single 0.95 1.7 25 10 Both Sides 2.0 3.5 26 11 Both Sides 2.0 0.1427 12 Both Sides 2.1 3.9 CE 11 11 Single 0.9 0.07 CE 12 12 Single 1.11.9 CE 13 6 Both Sides 2.2 3.8 CE 14 7 Both Sides 2.5 4.4 CE 15 8 BothSides 2.3 3.9 CE 16 9 Both Sides 2.3 4.0

indicates data missing or illegible when filed

Part 5 Benzyl Acetate Testing

The holder assembly used for evaporation rate and performance testing ofa membrane consisted of a front clamp with a ring gasket, a back clamp,test reservoir cup and four screws. The test reservoir cup wasfabricated from a clear thermoplastic polymer, having interiordimensions defined by a circular diameter at the edge of the open faceof approximately 4 centimeters and a depth of no greater than 1centimeter. The open face was used to determine the volatile materialtransfer rate.

Each clamp of the holder assembly had a 1.5″ (3.8 cm) diameter circularopening to accommodate the test reservoir cup and provide an opening toexpose the membrane under test. When placing a membrane under test,i.e., a sheet of microporous material having a thickness of from 6 to 18mils, the back clamp of the holder assembly was placed on top of a corkring. The test reservoir cup was placed in the back clamp and chargedwith approximately 2 mL of benzyl acetate. An approximately 2″ (5.1 cm)diameter disk was cut out of the membrane sheet and placed directly overand in contact with the edge of the reservoir cup such that 12.5 cm² ofthe volatile material contact surface of the microporous sheet wasexposed to the interior of the reservoir.

The front clamp of the holder was carefully placed over the entireassembly, with the screw holes aligned and so as not to disturb themembrane disk. When a coated microporous sheet was used, the coatedsurface was placed either toward the reservoir or toward the atmosphereas indicated in the Table below. The screws were attached and tightenedenough to prevent leaking. The ring gasket created a seal. The holderwas labeled to identify the membrane sample under test. From 5 to 10replicates were prepared for each test. Five replicates of a Control(uncoated sample) was included for the coated Examples. For the Examplesin Table 11, there were 5 Controls for each Example and the averageevaporation rate for each Control was reported with the correspondingExample as well as the percent reduction in evaporation rate of theexample compared to the corresponding Control. The coated surface ofExample 19-23 in Table 11 was towards the atmosphere.

Each holder assembly was weighed to obtain an initial weight of theentire charged assembly. The assembly was then placed, standing upright,in a laboratory chemical fume hood having approximate dimensions of 5feet (height)×5 feet (width)×2 feet (depth). With the test reservoirstanding upright, benzyl acetate was in direct contact with at least aportion of the volatile material contact surface of the microporoussheet. The glass doors of the fume hood were pulled down, and the airflow through the hood was adjusted so as to have eight (8) turns (orturnovers) of hood volume per hour. Unless otherwise indicated, thetemperature in the hood was maintained at 25° C.±5° C. The humiditywithin in the fume hood was ambient. The test reservoirs were regularlyweighed in the hood. The calculated weight loss of benzyl acetate, incombination with the elapsed time and surface area of the microporoussheet exposed to the interior of the test reservoir, were used todetermine the volatile material transfer rate of the microporous sheet,in units of mg/(hour*cm²). The average evaporation rate (mg/hr) of thereplicates was reported for the entire assembly in the Tables below.These two values are related by the following formula:

Average evaporation rate (mg/hr)/12.5 cm²=Volatile Material transferrate (mg/hour*cm²)

Marginal (Marg.) indicates that there were both passing and failingreplicates or that the test had no failures as described by “pooling”and “dripping” of the benzyl acetate down the surface of the membranebut had some drops of benzyl acetate forming beads on the surface of themembrane, which was also unacceptable.

TABLE 9 Samples Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 CE1 CE 2 CE 3 CE 4 CE 5 5 Day Results Pass Pass Pass Pass Pass Pass PassPass Pass Fail Fail Fail Fail Fail Evaporation rate 2.8 2.8 2.6 2.8 2.74.3 3.2 3.3 3.2 3.0 3.1 2.9 2.6 2.8

TABLE 10 Samples Ex. 10 Ex. 11 Ex. 12 Ex 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17Ex. 18 CE 6 CE 7 CE 8 CE 9 CE 10 5 Day Results Marg. Marg. Marg. Marg.Pass Pass Pass Pass Pass Fail Fail Fail Fail Fail Evaporation Rate 3.43.3 3.2 3.2 3.7 3.9 3.7 3.8 3.7 2.9 3.0 3.0 3.3 3.1

TABLE 11 Samples Ex. 19 Control Ex. 20 Control Ex. 21 Control Ex. 22Control Ex. 23 Control 5 Day Results Pass Fail Pass Fail Pass Fail PassFail Pass Fail Evaporation rate 4.09 4.65 3.61 4.69 2.05 4.10 2.68 4.691.25 4.03 Percent Reduction in 12 23 50 46 69 Evaporation Rate

TABLE 12 Ex. 24 Ex. 24 CE 11 CE 12 Samples Contool⁽¹⁾ Ctr⁽²⁾ Cta⁽³⁾ Ex.25 Control⁽⁴⁾ Ex. 26 Ex. 27 Cta⁽³⁾ Cta⁽³⁾ CE 13 CE 14 CE 15 CE 16 5 DayResults Fail Pass Pass Pass Fail Pass Pass Fail Fail Fail Fail Fail FailEvaporation Rate 2.64 2.64 2.61 2.83 3.4 3.3 3.4 3.3 3.2 2.64 2.63 2.562.65 ⁽¹⁾Control of uncoated TESLIN ® HD microporous material that wasincluded with Examples 24, 25, CE 13-16. ⁽²⁾Coated surface was directedtoward reservoir of volatile material. ⁽³⁾Coated surface was directedtoward the atmosphere. ⁽⁴⁾Control of uncoated TESLIN ® HD microporousmaterial that was included with Examples 26, 27, CE 11-12.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

1. A microporous material comprising: (a) a matrix of substantiallywater-insoluble thermoplastic organic polymer comprising polyolefin; (b)finely divided, substantially water-insoluble particulate filler, saidparticulate filler being distributed throughout said matrix andconstituting from 40 to 90 percent by weight, based on the total weightof said microporous material; and (c) a network of interconnecting porescommunicating substantially throughout said microporous material;wherein said microporous material has, a density of at least 0.8 g/cm³,a volatile material contact surface, a vapor release surface, whereinsaid volatile material contact surface and said vapor release surfaceare substantially opposed to each other, and a volatile materialtransfer rate, from said volatile material contact surface to said vaporrelease surface, of from 0.04 to 0.6 mg/(hour*cm²), and wherein whenvolatile material is transferred from said volatile material contactsurface to said vapor release surface, said vapor release surface issubstantially free of volatile material in liquid form.
 2. Themicroporous material of claim 1 wherein said microporous material has adensity of from 0.8 to 1.2 g/cm³.
 3. The microporous material of claim 1wherein said volatile material transfer rate is from 0.30 to 0.55mg/(hour*cm²).
 4. The microporous material of claim 1 wherein saidvolatile material transfer rate is from 0.35 to 0.50 mg/(hour*cm²). 5.The microporous material of claim 1 wherein said volatile materialcontact surface and said vapor release surface are each free of acoating material.
 6. The microporous material of claim 1 wherein atleast a portion of said volatile material contact surface has a firstcoating thereon, and/or at least a portion of said vapor release surfacehas a second coating thereon.
 7. The microporous material of claim 6wherein said first coating and said second coating each independently isformed from an aqueous coating composition selected from the groupconsisting of aqueous poly(meth)acrylate dispersions, aqueouspolyurethane dispersions, aqueous silicon oil dispersions, andcombinations thereof.
 8. The microporous material of claim 7 whereineach aqueous coating composition has a particle size of from 200 to 400nm.
 9. The microporous material of claim 8 wherein said first coatingand said second coating each independently have a coating weight of from0.01 to 5.5 g/m².
 10. The microporous material of claim 1 wherein saidpolyolefin comprises ultrahigh molecular weight polyethylene having anintrinsic viscosity of at least 10 deciliters/gram.
 11. The microporousmaterial of claim 10 wherein said ultrahigh molecular weight polyolefinis ultrahigh molecular weight polyethylene having an intrinsic viscosityof at least 18 deciliters/gram.
 12. The microporous material of claim 11wherein said ultrahigh molecular weight polyethylene has an intrinsicviscosity in the range of from 18 to 39 deciliters/gram.
 13. Themicroporous material of claim 1 wherein said polyolefin comprises amixture of substantially linear ultrahigh molecular weight polyethylenehaving an intrinsic viscosity of at least 10 deciliters/gram and lowermolecular weight polyethylene having an ASTM D 1238-86 Condition E meltindex of less than 50 grains/10 minutes and an ASTM D 1238-86 ConditionF melt index of at least 0.1 grams/10 minutes.
 14. The microporousmaterial of claim 13 wherein said substantially linear ultrahighmolecular weight polyethylene constitutes at least one percent by weightof said matrix and said substantially linear ultrahigh molecular weightpolyethylene and said lower molecular weight polyethylene togetherconstitute substantially 100 percent by weight of the polymer of thematrix.
 15. The microporous material of claim 14 wherein said lowermolecular weight polyethylene comprises high density polyethylene. 16.The microporous material of claim 1 wherein said particulate fillerconstitutes from 20 to 90 percent by weight of said microporousmaterial, based on the total weight of said microporous material. 17.The microporous material of claim 16 wherein said particulate fillercomprises siliceous particles comprising particulate silica.
 18. Themicroporous material of claim 17 wherein said particulate silicacomprises particulate precipitated silica.
 19. The microporous materialof claim 1 wherein said pores constitute from 35 to 95 percent by volumeof said microporous material, based on the total volume of saidmicroporous material.
 20. A microporous material comprising: (a) amatrix of substantially water-insoluble thermoplastic organic polymercomprising polyolefin; (b) finely divided, substantially water-insolubleparticulate filler, said particulate filler being distributed throughoutsaid matrix and constituting from 40 to 90 percent by weight, based onthe total weight of said microporous material; and (c) a network ofinterconnecting pores communicating substantially throughout saidmicroporous material; wherein said microporous material has, a densityof less than 0.8 g/cm³, a volatile material contact surface, a vaporrelease surface, wherein said volatile material contact surface and saidvapor release surface are substantially opposed to each other, wherein(i) at least a portion of said volatile material contact surface has afirst coating thereon, and/or (ii) at least a portion of said vaporrelease surface has a second coating thereon, and a volatile materialtransfer rate, from said volatile material contact surface to said vaporrelease surface, of from 0.04 to 0.6 mg/(hour*cm²), and wherein whenvolatile material is transferred from said volatile material contactsurface to said vapor release surface, said vapor release surface issubstantially free of volatile material in liquid form.
 21. Themicroporous material of claim 20 wherein said microporous material has adensity of from 0.4 g/cm³ to less than 0.8 g/cm³.
 22. The microporousmaterial of claim 20 wherein said microporous material has a density offrom 0.40 g/cm³ to 0.7 g/cm³.
 23. The microporous material of claim 20wherein said volatile material transfer rate is from 0.30 to 0.55mg/(hour*cm²).
 24. The microporous material of claim 20 wherein saidvolatile material transfer rate is from 0.35 to 0.55 mg/(hour*cm²). 25.The microporous material of claim 20 wherein said first coating and saidsecond coating each independently is formed from an aqueous coatingcomposition selected from the group consisting of aqueouspoly(meth)acrylate dispersions, aqueous polyurethane dispersions,aqueous silicon oil dispersions, and combinations thereof.
 26. Themicroporous material of claim 25 wherein each aqueous coatingcomposition has a particle size of from 200 to 400 nm.
 27. Themicroporous material of claim 26 wherein said first coating and saidsecond coating each independently have a coating weight of from 0.1 to 3g/m².
 28. The microporous material of claim 20 wherein said polyolefincomprises ultrahigh molecular weight polyethylene having an intrinsicviscosity of at least 10 deciliters/gram.
 29. The microporous materialof claim 28 wherein said ultrahigh molecular weight polyolefin isultrahigh molecular weight polyethylene having an intrinsic viscosity ofat least 18 deciliters/gram.
 30. The microporous material of claim 29wherein said ultrahigh molecular weight polyethylene has an intrinsicviscosity in the range of from 18 to 39 deciliters/gram.
 31. Themicroporous material of claim 20 wherein said matrix comprises a mixtureof substantially linear ultrahigh molecular weight polyethylene havingan intrinsic viscosity of at least 10 deciliters/gram and lowermolecular weight polyethylene having an ASTM D 1238-86 Condition E meltindex of less than 50 grams/10 minutes and an ASTM D 1238-86 Condition Fmelt index of at least 0.1 grams/10 minutes.
 32. The microporousmaterial of claim 31 wherein said substantially linear ultrahighmolecular weight polyethylene constitutes at least one percent by weightof said matrix and said substantially linear ultrahigh molecular weightpolyethylene and said lower molecular weight polyethylene togetherconstitute substantially 100 percent by weight of the polymer of thematrix.
 33. The microporous material of claim 32 wherein said lowermolecular weight polyethylene is high density polyethylene.
 34. Themicroporous material of claim 20 wherein said particulate fillerconstitutes from 20 to 90 percent by weight of said microporousmaterial, based on the total weight of said microporous material. 35.The microporous material of claim 34 wherein said particulate fillercomprises siliceous particles comprising particulate silica.
 36. Themicroporous material of claim 35 wherein said particulate silicacomprises particulate precipitated silica.
 37. The microporous materialof claim 20 wherein said pores constitute from 35 to 95 percent byvolume of said microporous material, based on the total volume of saidmicroporous material.